Mercury vapor tube



NOV. 18, 1947. E, wHlTE 2,431,152

MERCURY VAPOR TUBE Filed March 1, 1945 INVENTOR J. E. WH/FE I BYWAMMATTORN EY Patented Nov. 18, 1947 UNITED STATE S PATENT OFFlC E MERCURYVAPGR TUBE John E. White, Bloomfield, N; J assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation of"Pennsylvania Application Marchl, 1945, Serial No. 580,356

3 Claims.

This invention relates to mercury vapor tubes and has particularapplication with respect to ignitrons.

Mercury vapor tubes, such as ignitrons and mercury arc rectifiers, havefrequently experienced trouble, such as arc-back and slow de-ionization.which ispartially due to excessive vapor density. 'Ilhus, therating ofmercury vapor tubes is often limited by the efficiency with whichmercury vapor in the tubes is condensed. Th body or en" velope portionof ignitrons is at present made of steel or steel alloy, and it has beendetermined that condensation eiiiciency in commercial tubes is generallyless than ten percent. This circumstance readily accounts for theexcessive vapor density prevailing in ignitrons in use.

Generally viewed, this invention has for an object the reduction ofvapor density in mercury vapor tubes.

Likewise from a broad aspect, the invention has for an object to improvethe efficiency of the vapor condensation in a mercury vapor tube.

More specifically, an object of the invention is to provide means aidingcondensation of mercury vapor in a steel or steel alloy container.

Other objects of the invention will appear to those skilled in the artto which it appertains as the description progresses, both by directrecitation thereof and by inference from the context.

For aid in readily understanding the invention and its application inthe art a drawing accompanies this specification, the single viewwhereof illustrates in longitudinal vertical section an ignitron whereinmy invention is incorporated.

In said drawing the general ignitron structure shown comprises a steelor steel alloy body or envelope constituted essentially by a cylindricalwall or portion In closed at top and bottom by headers H, I2, welded orotherwise secured to the cylindrical wall so as to form a vacuumtightenclosure. From the upper head I l is suspended, with interposedinsulation, an anode l3. Through the bottom header l2, likewise withinterposed. insulation, is a lead-in connection M by which current isconducted to an ignitor 15, a part of which is submerged in a mercurypool l5 covering the bottom header with appropriate depth. The pool l6constitutes a reconstructing cathode, and it will be appreciated thatare discharge between the cathode and anode, as well as between theignitor and the cathode, creates heat and vaporizes some of the mercury.Obviously as more and more mercury vaporizes, and in the absence ofequal condensation, the vapor density within the body or envelopeincreases. Such in- 2 crease of vapor density is undesirable, as it iswell known that the successful operation of mercury vapor tubes isstrongly dependent on the vapor density being. kept low.

To promote condensation, as well as to carry oif undesired heat, it iscommon practice toprovide a jacket l'l'for circulation of acoolingmedium around the envelope. Heat transfer thereby effected is ofcourse helpful, but even with the most efficient operation of thecooling medium, the condensation efiiciency in commercial tubes still isexceedingly low. This apparently is due to a considerable extent to thecharacter of the surface where condensation is intended to be efiected.Under ideal conditions, the mercury atoms reaching the surface would allbe condensed and none be reflected; but, unfortunately, that idealcondition is far from the fact in practice, and such a great portion ofreflection of the mercury atoms takes place that the ten per centefficiency mentioned above is a common and prevailing circumstance. Thedesideratum to be accomplished, therefore, is to obtain an inner surfacefor the cylindrical wall of the envelope, which will retain the mercuryatoms more effectively and deter reflection.

According to the present invention, the desired objective isaccomplished by coating the envelope wall, as at l8, with zirconium,which I find greatly promotes the condensation of the mercury vapor andprovides a surface deterring reflection of the mercury atoms. Thecooling system is adequate for extraction of the heat from all mercuryatoms which lodge and remain upon the surface, and since a much greaterproportion thus lodg and remain on the zirconium coated surface thanoccurs with an uncoated steel or steel alloy surface, the resultantefficiency of condensation of the mercury vapor is enhanced many fold.

Zirconium as the coating surface is of especial benefit in thatzirconium does not, amalgamate with mercury and therefore is neitherinjurious to the constituency of the pool or its vapor, nor does itdeteriorate and become less efiective in its condensing characteristicfrom use. Furthermore, the zirconium functions advantageously as acorrosion resistant, has high thermal emissivity and serves incidentallyin assisting in the cleaning up of foreign gas in th envelope by virtueof the gettering properties inherent in zirconium.

The zirconium may be applied in various ways, of which may be mentionedapplication thereof by mixing either the metal or a compound of themetal, such asthe hydride, with a nitrocellulose 3 binder and painting,spraying or otherwise applying the same to said wall or its surface. Thecoating I8 may likewise be accomplished by electroplating zirconium onthe envelope wall. Inclusion of zirconium in the alloy of which saidenvelope wall is composed is likewise contemplated in the invention andis to be understood as included in the broad recitation of zirconiumapplied to said wall or its surface exposed to the interior of theenvelope.

I claim:

1. A mercury vapor tube having an envelope on a wall whereof mercury iscondensed in use, mercury in said envelope, means for vaporizing themercury, and zirconium on said Wall exposed to the interior of theenvelope for assisting in condensation of the vaporized mercury.

2. A mercury Vapor tube having an envelope on a wall whereof mercury iscondensed in use, mercury in said envelope, means vaporizing themercury, and a coating containing zirconium n the surface of said wallexposed to the interior of the envelope for promoting condensation ofthe vaporized mercury impinging on said coating.

3. A mercury vapor tube having an envelope providing a cylindrical walland headers at top and bottom thereof and sealed thereto, a cathode poolof mercury on the bottom header, an anode 4 suspended from the topheader, said cathode and anode adapted to sustain an arc discharge bywhich mercury is caused to vaporize, and a coating of zirconium on theinside of said cylindrical wall exposed to the mercury vapor andassisting in condensation of said vapor.

JOHN E. WHITE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES U. S. Bureau of Mines, Bulletin186 (1921), pages 3-113. (Copy in the Scientific Library, TN23.U4.)

